Why did Caesar fail and Augustus succeed in establishing autocracy at Rome?
There are many reasons as to why Augustus succeeded, where Caesar failed, in establishing autocracy in Rome. Despite these many reasons, two areas are of particular significance. One of these areas is Augustus' ability to successfully deal with all of his possible enemies while Caesar did not. The other area is the presentation of each rulers rise to power to the Roman people and senate.
While Julius Caesar was a successful general, and was able to grasp his power successfully, he was unable to hold it due to his overlooking of closer enemies which led to his short rule and early death in 44 B.C. In contrast, Augustus succeeded in eliminating all enemies and secure his long rule over Rome.
In Caesars rise to power, he effectively eliminated his primary enemies, but did not recognize any less obvious sources of potential danger. Caesar had entered into the First Triumvirate, a secret pact between himself, Pompey and Crassus. The First Triumvirate was created to keep each of the members from opposing each other's political ambitions.
Although after the deaths of Crassus, and of Caesar's daughter Julia, tension arose between Pompey and Caesar. These tensions eventually led to the pact breaking down, Pompey and the Senate were first to break the pact by ordering Caesar to disband his legions.  Instead of disbanding his legions Caesar marched on Rome and was victorious in the battle for Rome. Pompey was forced to Egypt where he was in turn murdered. Caesar recognized that it was customary for a son to avenge his fathers death and furthermore that Pompey's two sons and their supporters had become a threat to him. Caesar killed Pompey's elder son and supporters in the Battle of Munda, Pompey's younger son was then forced to live by “piracy”
After eliminating his primary enemies Caesar felt secure enough to grant clemency to the remaining pompeians....